This application relates generally to magnetic disc drive assemblies and more particularly to a crash stop assembly for a disc drive.
Information is written to and read from tracks on disc drive discs through the use of a pivoting actuator assembly. The actuator assembly includes heads, which each move in close proximity above the corresponding surface of the associated disc. A voice coil motor controls the track position of the heads by pivoting the actuator assembly. The voice coil motor typically includes a coil attached to the actuator assembly, as well as one or more permanent magnets, which establish a magnetic field in which the coil is immersed. A bottom pole proximal the disc drive base plate and a top pole distal from the base plate typically establishes the magnetic field. The controlled application of current to the coil causes magnetic interaction between the permanent magnets and the coil so that the actuator assembly pivots.
Various approaches have been developed to securely position an actuator assembly in a disc drive during a loss of power event or shutdown of the drive such that the heads do not land on a portion of the disc real estate that contains data. Typically these approaches involve either positioning the actuator assembly onto a shelf to hold the heads away from the discs or positioning the heads over portions of the disc surfaces that contain no data, such as the landing zones of the discs. The landing zones typically contain no magnetic recorded information or alternatively contain only historical servo information that is not pertinent to drive operation if damaged by the heads actually contacting the surfaces of the discs in this location. Approaches for holding the arm assembly in such as xe2x80x9cparkxe2x80x9d position include mechanical latches, electromechanical latches and magnetic latches.
To limit the range of motion of the actuator and heads under loss of power conditions and keep the heads in the landing zone, designers usually incorporate crash stops and a latch mechanism to position and hold the arm in the park position while the drive is without power. One concern in providing a latch and crash stop assembly is the level of energy absorbed by the crash stops. It is desirable that the crash stops absorb the impact of the actuator assembly as it stops without detrimentally affecting the head disc interface, even though the actuator assembly is designed to stop in a position away from the data region of the discs where the heads are parked. If excessive impact were to occur, the heads or the disc surface itself could be damaged by head slap. Consequently, crash stops may incorporate some type of rubber or polymeric cushion and limit impact deflection to keep the heads from moving out of the landing zone onto the data region of the disc. Often rubber cushions have not produced repeatable energy absorption characteristics because, for example, temperature changes can significantly alter the stiffness characteristics of the rubber material.
Typically, the installation of an actuator assembly in a disc drive having a voice coil motor includes three steps: (1) the bottom pole of the voice coil magnet is mounted adjacent the base plate, (2) the actuator itself is installed with the voice coil adjacent the bottom pole, and (3) the top pole of the voice coil magnet is installed with the top pole adjacent the voice coil. Typically between steps 2 and 3 the latch is not operational and the crash stops are not fully installed. For example, a magnetic latch that operates by using the magnetic flux from the voice coil magnet may be installed with the bottom pole of the voice coil magnet. However, until the top pole of the voice coil magnet is installed, the magnetic flux will not be channeled through the magnetic latch and the latch will not be operational. Additionally, crash stops are often installed with the top pole of the voice coil magnet, and thus the magnetic stops are often not functional between steps 2 and 3.
With the crash stops and the latch not being functional between steps 2 and 3, the actuator may pivot out of position, which may cause the recording head to contact the disc in a position other than the park position or to contact other parts of the disc drive. This may damage the disc or the recording head.
Accordingly, there is a need for an improved crash stop assembly. The present invention provides a solution to this and other problems, and offers other advantages over the prior art.
Against this backdrop the present invention has been developed. An embodiment of the present invention is a crash stop assembly for limiting pivotal movement of an actuator assembly mounted on a base plate of a disc drive. The disc drive includes a signal channel extending from the actuator assembly to a disc drive circuit board, and the crash stop assembly includes a connector bracket secured to the base plate and supporting the signal channel. The crash stop assembly further includes a crash stop secured to the connector bracket and extending therefrom, and the crash stop includes a contact surface that contacts the actuator assembly to limit pivotal movement of the actuator assembly. In a preferred embodiment, the crash stop preferably is integrally formed with the connector bracket. The crash stop may limit pivotal movement of the actuator assembly in a first direction and the crash stop assembly may further include a second crash stop secured to the connector bracket and extending therefrom.
Stated another way, an embodiment of the present invention is a disc drive including a disc rotatably mounted on a base plate, and a pivotally supported actuator assembly mounted adjacent the disc on the base plate, and a read/write channel extending from the actuator assembly to a disc drive circuit board. The disc drive further includes a crash stop assembly for limiting pivotal movement of the actuator assembly. The crash stop assembly includes a connector bracket secured to the base plate and supporting the signal channel. The crash stop assembly further includes a crash stop secured to the connector bracket. The crash stop includes a contact surface that contacts the actuator assembly to limit pivotal movement of the actuator assembly.
The present invention can further be implemented as a disc drive including an actuator assembly pivotally mounted to a base plate of the disc drive and means for limiting pivotal movement of the actuator assembly to a predetermined range. In a preferred embodiment, the disc drive includes a signal channel extending from the actuator assembly to a disc drive circuit board, and the means for limiting pivotal movement comprises means for supporting the signal channel.
These and various other features as well as advantages which characterize the present invention will be apparent from a reading of the following detailed description and a review of the associated drawings.